What are oil pan bolts supposed to be torqued to?

Which gasket, cork or rubber? Usually they are torqued until the pan bends a bit and leaks between all the bolts, that is the way I see a lot of them.

cork.

Merc Manual from 89, not sure if they used cork in 89 or not.

1/4 - 20 80 in. lbs.
5/16 - 18 165 in. lbs.

I would not tighten any more than what just barely deflects the pan. Watch it closely or use a straight edge. A softer gasket will take less torque. Each brand of cork gasket will compress differently. Take your pick on sealants.

I'd use rubber gaskets personally, Make sure you tighten them in a cross patern not in a row.

Tighten them till they strip and then back a quarter turn! Actually, I use a nut -driver and tighten about as tight as I can in a cricc-cross pattern and usually have no leaks.

Tighten until the gasket starts to push out and stop there.

Cast or stamped pan?

f31, its stamped